The Dallas Mavericks announced today that Dirk Nowitzki underwent arthroscopic surgery to his right knee. The surgery was performed at Texas Sports Medicine by team orthopedic surgeon T.O. Souryal. Nowitzki is expected to resume on-court activities within approximately 6 weeks.

Good for development of younger players who will have to step up. Also while Brand isn't anywhere near all star anymore he's still very capable of holding it down while Dirk is gone. The guy is still a tier 1 defensive PF just a step below KG.

This could be a blessing in disguise for the Mavs.
First, because Dirk holding out surgery would've been a really terrible decision in the long run.
Secondly, because it'll force his teammates, particularly the newer guys, to step up, making the team stronger overall.